Stomata are tiny apertures or pores in the leaf epidermis, which allows CO2/O2 exchange to control the process of photosynthesis. Both photosynthesis and the gas exchange that powers it are essential to the plant's survival. Opening and closure of stomata are important mechanisms that plants use to control the diffusion of gases in and out of leaves. Ideally, stomata must be sufficiently open to allow enough CO2 (needed for photosynthesis) to diffuse in, but sufficiently closed to prevent too much evaporative loss of H2O. This is sometimes a difficult balance to achieve and the amount of stomata opening is controlled by a large number of factors.
There is a great interest in the scientific community to measure the dimensions, frequency, density and rates of gas exchange of these natural openings. To date, indirect methods using image processing, are the most commonly used to measure stomata dimensions. A picture is usually taken under a microscope and measurements are done on leaf imprints. It is crucial to note that leaf damage is usually the result of such techniques. This, in turn, will affect the leaf structure and more likely the stomata measurements. Stomata dimensions are usually done on a screen using image-editing packages, such as ImageJ and MultiSpec. The most advanced and widely adopted method has been used to estimate stomata openings by indirectly assessing leaf gas exchange potentials. This sophisticated indirect method involves very expensive and bulky apparatus such as LICOR6400 Portable Photosynthesis and Fluorescence System. Less sophisticated apparatus such as the portable CI-340 Handheld Photosynthesis System (CID, 2015) has been promoted as a surrogate method to assess stomata efficiency in gas exchange. These types of instruments measure attributes such as photosynthesis, transpiration, stomata conductance, and internal CO2 concentration in open or closed environments.
So far, the current technologies failed to suggest a direct and precise measurement techniques to accurately detect the stomata in the epidermis of a plant leaf and to precisely measure parameters and/or dimensions thereof.